In general, when extruding a metal material, for example, a billet of aluminum or an alloy material of the same, by an extrusion press, the following apparatus is used for the extrusion. An extrusion stem is attached to a front end part of a main ram driven by a hydraulic cylinder. In a state with a container pressed against a die stack, the billet is placed in the container by the extrusion stem etc. Further, the main ram is made to further advance by the drive operation of the hydraulic cylinder. Due to this, the billet is pushed by the extrusion stem. Therefore, a shaped product is extruded from an outlet part of the die stack.
In the shear device of the extrusion press of PLT 1, to maintain the sharpness of the shear knife, it was necessary to sufficiently fasten the die stack. For this reason, the practice had been to use something like a hydraulic cylinder. If using a hydraulic cylinder or other hydraulic circuit, there was trouble such as degradation of the hydraulic fluid and leakage of fluid from the piping joints. This causes a problem in terms of the environment and maintenance costs. Also, there was an accompanying risk of fire at the time of operation and time of maintenance. Further, to fasten the die stack in the horizontal direction or vertical direction and make a shear slide engage in a rocking motion, a large hydraulic force was required from the hydraulic cylinder, so the drive device became larger.